This is de-classified test footage from the 1946 Bikini Atoll tests by the United States. The tests were conducted partly to ascertain the effects of a nuclear underwater 'burst' on a port or harbour facility - New York, for example. I think the actual device tested here was a fission -- 'atom bomb' of the type detonated over Nagasaki in Japan in 1945 - a slightly improved version of the Plutonium 'Fat Man' type bomb.with a very similar 'yield' of about 22 kilotonnes of TNT. I think the tested device (or bomb) was actually placed on board a decommissioned US Navy ship and the other ships anchored nearby from this test footage were placed there deliberately to gauge the effects of blast, fire and radiation on solid objects in close proximity.
